I’ve looked at a few on fdroid and they all seem like they aren’t being maintained anymore.
Edit: I’ve spent the past day trying most all of the suggested keyboards here and I think I’ve landed on either Unexpected Keyboard or AnySoftKeyboard. Thanks for all the suggestions. Thumbkey is quite the thing to get used to.
I won’t pretend to know how tightly integrated the keyboard is within the Android OS, but given the interoperability between app and keyboard it seems likely that vulnerabilities could be leveraged to gain malicious access to the clipboard and other sensitive data.
Probably that would be an Android vulnerability.